> We don’t share tech stacks, but we do work together, and as you can imagine that leads to wasted resources. We’re a C# shop our direct neighbour does PHP, because of limited resources, we can’t utilise each others projects. That’s just a silly waste. Good luck convincing anyone to change their overall and often cohesive strategy for tech choices though.

One suggestion, if you don't mind. When I did work for the DoD as a contractor, because of small business rules in government contracting we were pretty much forced to work with at least 10 other companies and all of them had their own preferences for tech stacks, their own expertise, etc. So we tried to go down the road of using things like thirft or avro so regardless of what language / stack you used, as long as you could interface with those on the same network (since we're talking about inter-service communication here) it was still pretty quick.

It's not ideal but sometimes you gotta work with what you have. Sometimes you can find unique ways to bridge gaps across platforms to re-use work. One time a group we worked with tried to use a web app with multiple iframes as the communication bridge between stacks. It _worked_ but it was pretty hacky and slow.